Such an assembly is, for example, known from U.S. Pat. No. 5,482,444, issued to Coha et al. in 1996, corresponding to EP-A-0 701 058. A plastic reservoir—providing a stationary support—is fixed to the bottom of a fuel tank. A generally cylindrical electric fuel pump is received in a plastic inner retainer, which is itself fitted in the plastic reservoir. The inner retainer is provided with two flexible legs extending vertically from its upper edge. These flexible legs are each provided at their upper end with a barb thereon, which engages in a notch in the reservoir to firmly attach the inner retainer to the reservoir. To minimise the transmission of vibrations of the fuel pump to the fuel tank, the fuel pump is surrounded by an elastic sleeve in the inner retainer. The elastic sleeve includes a plurality of small diameter elastic tubes, which extend longitudinally and are tangent to the sleeve. The small elastic tubes are integral with the elastic sleeve and are seated in corresponding channels in the inner retainer, whereby the resilient reactions of each of the elastic tubes on the fuel pump cooperate in suspending the fuel pump relative to the reservoir. Furthermore, vibratory excursions of the fuel pump are resiliently resisted by the elastic tubes, so that fuel pump vibrations are isolated from the reservoir.